Recent advances in tunable metal–support interactions for enhancing the photocatalytic nitrogen reduction reaction

Ammonia (NH3), as an important foundational chemical and green hydrogen energy carrier, plays an indispensable role in the development of human society. However, it is evident that the traditional process for NH3 synthesis is no longer in line with the times due to its drawbacks, such as high energy consumption and high carbon emission. In recent years, the photocatalytic nitrogen reduction reaction (PNRR), which reduces N2 to NH3 under mild conditions using inexhaustible solar energy, has been considered as a promising alternative. Nevertheless, the catalytic efficiency of the PNRR is low and far from realizing practical applications owing to the weak N2 adsorption, hard dissociation of inert NN, and competing reactions of hydrogen precipitation. Metal–support interactions (MSIs) provide an efficient way to adjust the performance of both the active metal and support in the photocatalytic process through geometric, electronic and bifunctional effects. The design of heterogeneous photocatalysts with tunable MSIs has been proved to be a feasible way to enhance their catalytic performance for the PNRR. In this review, we summarize the recent developments in MSI photocatalysts involved in nitrogen fixation. Firstly, the mechanism of MSIs and their characterization as well as the synthesis strategies for photocatalysts with MSIs are briefly outlined. Subsequently, the electronic and bifunctional effects of MSI photocatalysts and the corresponding PNRR mechanism are focused on, from the aspects of supports such as metal oxides, bismuth oxyhalides, metal sulfides, metal–organic frameworks (MOFs) and carbon nitrides. Finally, the future developments in this area such as creating state-of-the-art materials with MSIs and synthesis strategies and developing advanced techniques to investigate reaction mechanisms for N2 fixation are discussed. It is expected that this review can provide some guidance for understanding and rationally designing MSI photocatalysts, especially for boosting the PNRR.